I work on Linux all the time and I'm clueless about Windows not even having one to try it, is Git nowadays working on Windows? or am I making problems for my Windows-pals by using it?
It works, but not well. If you Google around a bit, you'll find the port which uses MinGW. The main problems are instability and some very Linux-like tools (gittk). If you really need it though, you should be able to get by.
As far as I can tell msysgit works perfectly well under Windows Vista.
This after a whole 2-month experience checking out plugins and applications for Ruby on Rails :-)
Anyway, it was a breeze to install, no problem.
I have had no problems, even with the gui tools (gitk and git gui), using git from Cygwin. The Cygwin people are very conscientious and have a large community to boot.
You should also checkout Git-Extensions which adds git commands as shell extensions - works great with msysgit.
I've heard good things about it, but a sticking point for me (and the Japanese company I work for) is lack of cross-platform Unicode filename support. It depends if that particular feature is important to you.
See Issue 80 in the msysgit bug tracker.
See the What DVCS support Unicode filenames? question I asked about this.